System-on-chip (SoC) integrated circuits (ICs), which combine multiple very large scale integration (VLSI) designs in a single chip, have become very popular in digital industries, including telecommunications and mechanical controlling. In addition, SoCs have become essential in the healthcare field, especially for life-saving implanted devices, such as pacemakers. In SoCs, a variety of circuits can be incorporated into a single block instead of being built separately on multiple blocks, which reduces production time and cost. Most SoCs are based on complementary metal oxide semiconductor (CMOS) design concepts. CMOS-based circuits offer the advantages of high speed, low power consumption, immunity to harsh environments, and scalability. In addition, CMOS-based circuits provide better signal quality and better frequency response.
There are two types of power consumption in SoCs: static and dynamic power consumption. Due to leakage current, CMOS-based circuits have very low static power consumption. During switching, CMOS transistors operate complementary to each other, in which case dynamic power consumption is at a minimum. Because of the low power consumption of CMOS-based circuits, higher densities of transistors on a chip are possible, which can enable integration of more applications into a single SoC. Because of the reduced power consumption, today's SoCs generate less heat and need little or no cooling.
CMOS-based circuits can be operated in the near-threshold voltage (NTV) region in which power consumption is lowest. Such operation is desirable both in terms of reducing the power that must be supplied to operate a device as well as reducing the amount of heat generated by the device. Research has been performed in the area of NTV using ring oscillators based on an aspect ratio of metal-oxide semiconductor field-effect transistor (MOSFET) devices. This research presented a solution for preventing high power consumption of ICs in which voltage regulators were used to produce a constant output. While such voltage regulators were shown to be effective in terms of controlling voltage output, they also resulted in losses of power. It would be desirable to have a means for regulating voltage supplied to an IC, such as a SoC, that does not suffer from such losses of power.